Motor control centers, as well as other electrical equipment like switchgear, are equipped with draw-out type protective control devices such as fusible disconnect switches, circuit breakers, and fuse trucks. These control devices are inserted into individual cells or compartments within the center to establish mechanical and electrical contact with bus bars, load and line stabs, or similar electrical terminals.
Due to the size and weight of many control devices, they are usually mounted on a support frame with rails or rollers and slid into position. The control device module may include a pair of upstanding cradle arms that are attached to the racking mechanism which facilitates rolling or sliding the control device into engagement with the electrical power load lines in the cells of the control center.
This type of racking mechanism is well known in the art and is available from several manufacturers. For example, the Square D Company produces a line of DS type circuit breakers which operate in accordance with the above description. While the racking mechanism presently available performs well, it is unnecessarily costly and may include many separate parts that are disposed about the circuit device for performing various interlock functions to assure safe installation, operation, removal, and testing. Some racking mechanisms of other manufacturers occupy a substantial amount of space in the control device. Thus, other components and features of the control device are prevented from using this area.
Another problem has been on-site accessibility to electrical components which are mounted within the control device and within the interior space of the cell itself. To gain access to these components, the control device is usually removed entirely from cell. Only after completely disengaging the control device from the racking mechanism is sufficient space provided to access the electrical components mounted on the rear surface of the control device and on the rear panel of the cell.
There is a need for a space-saving, inexpensive, and simple assembly between the control device and the cell of the control center which does not interfere with the electrical components mounted therein or operation of the control center and the respective control devices.